Fluorescent material, light-emitting device, and method for producing fluorescent material

ABSTRACT

A method for producing a fluorescent material can be provided. The method includes preparing fluorescent material particles that contain a fluoride having a composition including Mn, at least one selected from the group consisting of alkali metal elements and NH 4   + , and at least one selected from the group consisting of Group 4 elements and Group 14 elements; causing at least one cation selected from rare-earth elements and a phosphate ion to come into contact with each other in a liquid medium containing the fluorescent material particles to obtain rare-earth phosphate-adhered fluorescent material particles including the fluorescent material particles to which the rare-earth phosphate is adhered; and separating the rare-earth phosphate-adhered fluorescent material particles from the liquid medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No.2016-068292, filed on Mar. 30, 2016, and Japanese Patent Application No.2017-027027, filed on Feb. 16, 2017, the disclosures of which are herebyincorporated by reference in their entirety.

BACKGROUND Technical Field

The present disclosure relates to a fluorescent material, alight-emitting device, and a method for producing the fluorescentmaterial.

Description of the Related Art

A light emitting diode (LED) is a semiconductor light-emitting element(hereinafter also referred to as “light-emitting element”) produced froma metal compound such as gallium nitride (GaN). Many types oflight-emitting devices that emit light of, for example, white color,incandescent bulb color, and orange color have been developed using sucha light-emitting element in combination with a fluorescent material.Such light-emitting devices emit, for example, white light as a mixtureof three primary colors of light. For example, light-emitting devicesthat emit white light by using a light-emitting element that emits bluelight and a fluorescent material that emits yellow light are used in avariety of applications, including general lighting, backlighting forliquid crystal displays, in-vehicle lighting, and displays.

Red fluorescent materials having an excitation band in the blue region,and an emission peak with a narrow half bandwidth are known. Examples ofsuch red fluorescent materials include fluoride fluorescent materialshaving a composition of K₂SiF₆:Mn⁴⁺. Improved methods for producingthese materials have been studied (e.g., JP 2012-224536).

SUMMARY

A first aspect of the present disclosure includes a method for producinga fluorescent material including preparing fluorescent materialparticles that contain a fluoride having a composition including Mn, atleast one selected from the group consisting of alkali metal elementsand NH₄ ⁺, and at least one selected from the group consisting of Group4 elements and Group 14 elements; causing at least one cation selectedfrom rare-earth elements and a phosphate ion to come into contact witheach other in a liquid medium containing the fluorescent materialparticles to obtain rare-earth phosphate-adhered fluorescent materialparticles including the fluorescent material particles to which therare-earth phosphate is adhered; and separating the rare-earthphosphate-adhered fluorescent material particles from the liquid medium.According to an embodiment of the present disclosure, a highly durablered light-emitting fluorescent material, a light-emitting deviceincluding such a fluorescent material, and a method for producing thefluorescent material can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a scanning electron microscope (SEM) image of an exemplaryfluorescent material according to an embodiment of the presentdisclosure.

FIG. 1B is a partially enlarged view of FIG. 1A.

FIG. 2A is an SEM image of a comparative fluorescent material.

FIG. 2B is a partially enlarged view of FIG. 2A.

FIG. 3 is a schematic cross-sectional view of an exemplarylight-emitting device according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

A first aspect of the present disclosure includes a method for producinga fluorescent material including preparing fluorescent materialparticles that contain a fluoride having a composition including Mn, atleast one selected from the group consisting of an alkali metal elementsand NH₄ ⁺, and at least one selected from the group consisting of Group4 elements and Group 14 elements; causing at least one cation selectedfrom rare-earth elements and a phosphate ion to come into contact witheach other in a liquid medium containing the fluorescent materialparticles to obtain rare-earth phosphate-adhered fluorescent materialparticles including the fluorescent material particles to which therare-earth phosphate is adhered; and separating the rare-earthphosphate-adhered fluorescent material particles from the liquid medium.

A second aspect of the present disclosure is a fluorescent materialincluding fluorescent material particles that contain a fluoride havinga composition including Mn, at least one selected from the groupconsisting of alkali metal elements and NH₄ ⁺, and at least one selectedfrom the group consisting of Group 4 elements and Group 14 elements, anda rare-earth phosphate arranged on the fluorescent material particles.

A third aspect of the present disclosure is a light-emitting deviceincluding a fluorescent member containing a fluorescent material and aresin, and a light-emitting element having a peak emission wavelength ina wavelength range of 380 nm to 470 nm. The fluorescent materialincludes a fluorescent material according to the second aspect of thepresent disclosure.

Light-emitting devices known in the art still need to be improved indurability for use in harsh environments, such as use for lighting.According to an embodiment of the present disclosure, a highly durablered light-emitting fluorescent material, a light-emitting deviceincluding such a fluorescent material, and a method for producing thefluorescent material can be provided.

A fluorescent material according to the present disclosure, a method forproducing the fluorescent material, and a light-emitting device will nowbe described. However, the embodiments described below are mere examplesfor embodying the technical concept of the present invention, and thepresent invention is not limited to these. The relationship between thecolor names and the chromaticity coordinates, the relationship betweenthe wavelength ranges of light and the color names of monochromaticlight, and others are in accordance with Japanese Industrial Standard(JIS) Z8110. As used herein, the term “step” means not only anindependent step but also a step which cannot be clearly distinguishedfrom the other steps but that can achieve the desired object. For theamount of each component contained in a composition, when a plurality ofsubstances corresponding to the component exist, the amount of thecomponent means the total amount of the substances present in thecomposition unless otherwise specified.

Method for Producing Fluorescent Material

The method for producing a fluorescent material according to a firstaspect of the present disclosure includes preparing fluorescent materialparticles that contain a fluoride having a composition including Mn, atleast one selected from the group consisting of an alkali metal elementand NH₄ ⁺, and at least one selected from the group consisting of Group4 elements and Group 14 elements (hereinafter also referred to as“preparation step”); causing at least one cation selected fromrare-earth elements and a phosphate ion to come into contact with eachother in a liquid medium containing the fluorescent material particlesto obtain rare-earth phosphate-adhered fluorescent material particlesincluding the fluorescent material particles to which the rare-earthphosphate is adhered (hereinafter also referred to as “adhesion step”,the particles to which the rare-earth phosphate is adhered is referredto as “rare-earth phosphate-adhered fluorescent material particles”);and separating the rare-earth phosphate-adhered fluorescent materialparticles from the liquid medium (hereinafter also referred to as“separation step”).

The fluorescent material is obtained by a specific method that causes arare-earth phosphate to adhere to fluorescent material particlescontaining a fluoride having a specific composition. A light-emittingdevice including the fluorescent material can be highly durable. Forexample, a light-emitting device may include a fluorescent member thatincludes the fluorescent material and a resin, and that covers alight-emitting element. Durability as used herein means that a declinein the output and a change in the chromaticity over time in such alight-emitting device that emits light is reduced even when a highelectric current is applied to the light-emitting element. Thus, theinitial performance of the light-emitting device is maintained over along period. In the light-emitting devices known in the art, the resinmay fail to sufficiently cure presumably by the influence of a componentcontained in the composition of the fluoride, for example, an alkalimetal. However, using the rare-earth phosphate-adhered fluoridefluorescent material particles may reduce the influence of thecomposition of the fluoride, and allow the resin included in thefluorescent member to sufficiently cure around its interface with thefluorescent material. This causes a better adhesion between thefluorescent material and the resin. The good adhesion may prevent thefluorescent material from separating from the resin even when the resinin the fluorescent member expands due to an increase in temperature ofthe light-emitting device operated at a high electric current. If thefluorescent material detaches from the resin in the fluorescent member,a space is formed between the fluorescent material and the resin. Such aspace may cause scattering of light around the interface, reducing theamount of the incident excitation light into the fluorescent material.This may eventually cause a decrease in the amount of light taken fromthe fluorescent material to the outside of the light-emitting device.

In an embodiment, the rare-earth phosphate is directly adhered to thefluorescent material particles in a liquid medium. This is considered tofurther improve adhesion between the fluorescent material and the resin,and thus a light-emitting device including the fluorescent material canbe highly durable.

Preparation Step

In the preparation step, fluorescent material particles that contain afluoride having a composition including Mn, at least one selected fromthe group consisting of alkali metal elements and NH₄ ⁺, and at leastone selected from the group consisting of Group 4 elements and Group 14elements are prepared. Such fluorescent material particles may beprepared by either appropriately selecting commercial products orproducing as desired.

The fluorescent material particles including a fluoride includes Mn, atleast one selected from the group consisting of alkali metal elementsand NH₄ ⁺, and at least one selected from the group consisting of Group4 elements and Group 14 elements in its composition, and preferablyincludes at least potassium (K) and silicon (Si) in its composition. Thefluoride preferably has a composition represented by formula (1):

A₂[M_(1−p)Mn⁴⁺ _(p)F₆]  (1)

In formula (1), A is at least one selected from the group consisting ofalkali metal elements and NH₄ ⁺; M is at least one selected from thegroup consisting of Group 4 elements and Group 14 elements; and psatisfies 0<p<0.2.

In formula (1), A is at least one selected from the group consisting ofalkali metal elements and NH₄ ⁺, and preferably at least one selectedfrom the group consisting of lithium (Li), sodium (Na), potassium (K),rubidium (Rb), cesium (Cs), and ammonium (NH₄ ⁺). Or A may include atleast K, and further include at least one selected from the groupconsisting of Li, Na, Rb, Cs, and NH₄ ⁺. Still more preferably, A is,for example, an alkali metal containing K as a main component. As usedherein, “containing K as a main component” means that the potassiumcontent of A in formula (1) is 80% by mol or more, preferably 90% by molor more, and more preferably 95% by mol or more.

In formula (1), M is selected from the group consisting of Group 4elements and Group 14 elements. In consideration of emission properties,M is preferably at least one selected from the group consisting oftitanium (Ti), zirconium (Zr), hafnium (Hf), silicon (Si), germanium(Ge), and tin (Sn). More preferably, M contains silicon (Si), or bothsilicon (Si) and germanium (Ge), and still more preferably M is composedof silicon (Si), or silicon (Si) and germanium (Ge).

When M contains silicon (Si), or silicon (Si) and germanium (Ge), atleast a portion of one of Si and Ge may be replaced with at least oneselected from the group consisting of Group 4 elements, which includeTi, Zr, and Hf, and Group 14 elements, which include C and Sn. In thatcase, the total Si+Ge content of M is preferably, for example, 90% bymol or more, and more preferably 95% by mol or more.

In formula (1), p satisfies 0<p<0.2. In consideration of emissionefficiency and emission intensity, p is, for example, 0.01 or more,0.015 or more, 0.02 or more, or 0.03 or more, and p is also, forexample, less than 0.2, 0.15 or less, or 0.1 or less. In addition, forexample, p preferably satisfies 0.01≦p<0.2, more preferably satisfies0.015≦p≦0.15, still more preferably satisfies 0.02≦p≦0.1, and furtherpreferably satisfies 0.03≦p=0.1.

The particle diameter of the fluorescent material particles is, forexample, as a volumetric average particle diameter, 1 μm or more, 5 μmor more, or 20 μm or more, and is also, for example, 100 μm or less or70 μm or less. The particle size distribution of the fluorescentmaterial particles preferably has a single peak in this range, and morepreferably has a narrow distribution width. Using the fluorescentmaterial particles having a volumetric average particle diameter equalto or greater than the lower limit may improve the emission intensityand the durability. Using the fluorescent material particles having avolumetric average particle diameter equal to or less than the upperlimit may improve the workability in producing a light-emitting device.The volumetric average particle diameter of the fluorescent materialparticles is a particle diameter (median size) determined by a laserdiffraction particle size analyzer (MASTER SIZER 2000 by MalvernInstruments).

The fluoride is an Mn⁴⁺-activated fluorescent material, and can emit redlight by absorbing visible light at short-wavelengths. The excitationlight which is visible light at short-wavelengths is preferably mainlyin the blue color region. Specifically, the excitation light preferablyhas a main peak wavelength in its intensity spectrum in the range of 380nm to 500 nm, more preferably in the range of 380 nm to 485 nm, stillmore preferably in the range of 400 nm to 485 nm, and particularlypreferably in the range of 440 nm to 480 nm. Setting the main peakwavelength in the range may improve emission efficiency of thefluorescent material.

The fluorescent material containing the fluoride preferably has a peakwavelength in its emission spectrum in the range of 610 nm to 650 nm.The half bandwidth of the emission spectrum is preferably narrow, andspecifically preferably 10 nm or less.

Adhesion Step

In the adhesion step, at least one cation selected from rare-earthelements (hereinafter also referred to as “rare-earth metal ion”) and aphosphate ion are caused to come into contact with each other in aliquid medium containing the prepared fluorescent material particles.This allows a rare-earth phosphate to adhere to the surfaces of thefluorescent material particles to yield rare-earth phosphate-adheredfluorescent material particles. Causing the rare-earth phosphate toadhere to the fluorescent material particles in a liquid medium isconsidered to allow the rare-earth phosphate to, for example, furtheruniformly adhere to the surfaces of the fluorescent material particles.

The liquid medium should dissolve phosphate ions and rare-earth metalions. The liquid medium preferably contains at least water because ionsare readily soluble in water. The liquid medium may further contain areducing agent, such as hydrogen peroxide; an organic solvent; a pHadjuster; or other agents as appropriate. Examples of the organicsolvent that may be contained in the liquid medium include alcohols,such as ethanol and isopropanol. Examples of the pH adjuster includebasic compounds, such as ammonia, sodium hydroxide, and potassiumhydroxide; and acidic compounds, such as hydrochloric acid, nitric acid,sulfuric acid, and acetic acid. When the liquid medium contains a pHadjuster, the pH of the liquid medium is, for example, 1 to 6, andpreferably 1.5 to 4. When the pH is equal to or greater than the lowerlimit, the rare-earth phosphate may sufficiently adhere to thefluorescent material particles. When the amount is equal to or less thanthe upper limit, deterioration of the emission properties of thefluorescent material may be reduced. When the liquid medium containswater, the water content of the liquid medium is, for example, 70% bymass or more, preferably 80% by mass or more, and more preferably 90% bymass or more.

The mass percentage of the liquid medium to the mass of the fluorescentmaterial particles is, for example, 100% by mass or more, or 200% bymass or more, and, for example, 1000% by mass or less, or 800% by massor less. When the mass percentage of the liquid medium is equal to orgreater than the lower limit, the rare-earth phosphate can moreuniformly adhere to the surfaces of the fluorescent material particles.When the mass percentage of the liquid medium is equal to or less thanthe upper limit, the adhesion rate of the rare-earth phosphate to thefluorescent material may further improve.

The liquid medium preferably contains a phosphate ion, and morepreferably contains water and a phosphate ion. When the liquid mediumcontains a phosphate ion, the prepared fluorescent material particlesand the liquid medium, and further a solution containing a rare-earthmetal ion may be mixed together to cause the phosphate ion to come intocontact with the rare-earth metal ion in the liquid medium containingthe fluorescent material particles. When the liquid medium contains aphosphate ion, the phosphate ion content of the liquid medium is, forexample, 1% by mass or more, and preferably 2% by mass or more, and, forexample, 10% by mass or less, and preferably 7% by mass or less. Whenthe phosphate ion content of the liquid medium is equal to or greaterthan the lower limit, the amount of the liquid medium is not excessive,and the elution of the composition components of the fluorescentmaterial is reduced. This allows the fluorescent material to maintaingood properties. When the phosphate ion content of the liquid medium isequal to or less than the upper limit, the rare-earth phosphate may moreuniformly adhere to the fluorescent material. Examples of the phosphateion include orthophosphate ion, polyphosphate (metaphosphate) ion,phosphite ion, and hypophosphite ion. Examples of the polyphosphate ioninclude linear polyphosphate ions, such as pyrophosphate ion andtripolyphosphate ion, and cyclic polyphosphate ions, such ashexametaphosphate ion.

To prepare a liquid medium containing the phosphate ion, a compoundintended to be used as a phosphate ion source may be dissolved in aliquid medium, or a solution containing a phosphate ion source may bemixed with a liquid medium. Examples of the phosphate ion source includephosphoric acid; metaphosphoric acid; alkali metal salts of phosphoricacid, such as sodium phosphate and potassium phosphate; alkali metalsalts of hydrogen phosphoric acid, such as sodium hydrogenphosphate andpotassium hydrogenphosphate; alkali metal salts of dihydrogen phosphoricacid, such as sodium dihydrogen phosphate and potassium dihydrogenphosphate; alkali metal salts of hexametaphosphoric acid, such as sodiumhexametaphosphate and potassium hexametaphosphate; alkali metal salts ofpyrophosphoric acid, such as sodium pyrophosphate and potassiumpyrophosphate; and ammonium salts of phosphoric acid, such as ammoniumphosphate.

The liquid medium preferably contains a reducing agent, more preferablycontains water and a reducing agent, and still more preferably containswater, a phosphate ion, and a reducing agent. Using a liquid mediumcontaining a reducing agent can effectively decrease precipitation of,for example, manganese dioxide derived from Mn⁴⁺, which is contained inthe fluoride of the fluorescent material particles. Any reducing agentcapable of reducing Mn⁴⁺, which may otherwise elute from the fluorideinto the liquid medium, may be contained in the liquid medium. Examplesof such a reducing agent include hydrogen peroxide, oxalic acid, andhydroxylammonium chloride. Of these, hydrogen peroxide is preferablebecause hydrogen peroxide dissolves in water, leaving no adverse effecton the fluoride.

To prepare a liquid medium containing the reducing agent, a compoundthat serves as the reducing agent may be dissolved in a liquid medium,or a solution containing the reducing agent may be mixed with a liquidmedium. The reducing agent content of the liquid medium is notparticularly limited. For the reasons described above, the reducingagent content is, for example, 0.1% by mass or more, and preferably 0.3%by mass or more.

Examples of the rare-earth element that forms a rare-earth metal ion tocome into contact with a phosphate ion include, in addition to Sc and Y,lanthanoid elements, which consist of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd,Tb, Dy, Ho, Er, Tm, Yb, and Lu. At least one selected from lanthanoidelements is preferable, and at least one selected from the groupconsisting of La, Ce, Dy and Gd is more preferable.

The phosphate ion and the rare-earth metal ion may be caused to comeinto contact with each other in a liquid medium, for example, bydissolving a compound that serves as a rare-earth metal ion source in aliquid medium containing the phosphate ion, or by mixing a liquid mediumcontaining the phosphate ion and a solution containing the rare-earthmetal ion. The solution containing the rare-earth metal ion can beprepared by, for example, dissolving a compound that serves as therare-earth metal ion in a solvent, such as water. The compound thatserves as the rare-earth metal ion source is, for example, a metal saltcontaining a rare-earth element. Examples of the anion to be included inthe metal salt include nitrate ion, sulphate ion, acetate ion, andchloride ion.

Causing the phosphate ion and the rare-earth metal ion to come intocontact with each other in a liquid medium may include, for example,mixing a liquid medium containing the phosphate ion, preferably furthercontaining the reducing agent with the fluorescent material particles toprepare a fluorescent material slurry; and mixing the fluorescentmaterial slurry with a solution containing the rare-earth metal ion.

The rare-earth metal ion content of a liquid medium in which thephosphate ion and the rare-earth metal ion are caused to come intocontact with each other is, for example, 0.05% by mass or more, or 0.1%by mass or more, and, for example, 3% by mass or less, or 2% by mass orless. The rare-earth metal ion content relative to the amount of thefluorescent material particles in the liquid medium is, for example,0.2% by mass or more, or 0.5% by mass or more, and, for example, 30% bymass or less, or 20% by mass or less. Using a liquid medium with arare-earth metal ion content being equal to or greater than the lowerlimit may allow the rare-earth phosphate to better adhere to thefluorescent material. Using a liquid medium with a rare-earth metal ioncontent being equal to or less than the upper limit may allow therare-earth phosphate to more readily uniformly adhere to the surfaces ofthe fluorescent material particles.

The temperature at which the phosphate ion and the rare-earth metal ionfor forming the rare-earth phosphate are caused to come into contactwith each other is, for example, 10° C. to 50° C., and preferably 20° C.to 35° C. The duration of contact is, for example, 1 min to 1 hour, andpreferably 3 min to 30 min. The contact may be carried out whilestirring the liquid medium.

Separation Step

In the separation step, the resulting rare-earth phosphate-adheredfluorescent material particles are separated from the liquid medium toyield a desired fluorescent material. The separation may be carried outusing, for example, solid-liquid separation means, such as filtering andcentrifugal separation. The fluorescent material obtained through thesolid-liquid separation may undergo treatments such as washing anddrying as appropriate. The washing treatment may be carried out using,for example, an alcohol, such as ethanol or isopropyl alcohol; a ketonicsolvent, such as acetone; or water. The drying treatment may be carriedout at room temperature, or with heating. The heating in the dryingtreatment may be carried out, for example at a temperature of 95° C. to115° C. The duration of the drying may be, for example, 8 hours to 20hours.

Fluorescent Material

The fluorescent material according to a second aspect of the presentdisclosure includes fluorescent material particles containing a fluoride(hereinafter also referred to as “core particles”) and a rare-earthphosphate arranged on the fluorescent material particles. The fluoridehas a composition including Mn, at least one selected from the groupconsisting of alkali metal elements and NH₄ ⁺, and at least one selectedfrom the group consisting of Group 4 elements and Group 14 elements.Arranging the rare-earth phosphate on the fluorescent material particlesmay improve, for example, adhesion or cohesion between the fluorescentmaterial and the resin in a fluorescent member included in alight-emitting device. Improved adhesion or cohesion allows thelight-emitting device to be more durable.

The details of the fluorescent material particles containing thefluoride, and the rare-earth phosphate included in the fluorescentmaterial are as described above. In the fluorescent material, therare-earth phosphate is adhered to and arranged on the core particles.The adhesion of the rare-earth phosphate to the core particles may becarried out by means of, for example, a physical interaction, such asvan der Waals force or a static interaction, or a chemical interactioncaused by a partial chemical reaction. The rare-earth phosphate may beadhered to the core particles in the form of a film or particles. Inconsideration of durability, at least a part of the rare-earth phosphateis preferably adhered to the core particles in the form of a film. Asused herein, the rare-earth phosphate being arranged in the form of afilm means that 50% or more, preferably 70% or more of the area of thesurfaces of the core particles is covered with the rare-earth phosphate.

The amount of the rare-earth phosphate arranged on the core materials inthe fluorescent material is, for example, 0.05% by mass or more, 0.1% bymass or more, 0.5% by mass or more, 0.8% by mass or more, 1% by mass ormore, or 2% by mass or more in terms of the rare-earth metal elementcontent. The rare-earth metal element content is also, for example, 20%by mass or less, 16% by mass or less, 14% by mass or less, 10% by massor less, or 8% by mass or less. When the amount of the rare-earthphosphate arranged is equal to or greater than the lower limit, thefluorescent material may be durable enough. When the amount of therare-earth phosphate arranged is equal to or less than the upper limit,deterioration of the emission properties of the fluorescent material maybe reduced.

The rare-earth metal element content and the phosphate ion contentincluded in the rare-earth phosphate in the fluorescent material can bedetermined by ICP-AES (high-frequency inductively coupled plasmaemission spectral analysis method).

The particle diameter and the particle size distribution of thefluorescent material reflect the characteristics of the particlediameter and the particle size distribution of the core particles. Theparticle diameter of the fluorescent material is, for example, 1 μm ormore, 5 μm or more, or 20 μm or more, and, for example, 100 μm or less,or 70 μm or less. The fluorescent material having a particle diameterequal to or greater than the lower limit may have improved emissionintensity and durability. The fluorescent material having a particlediameter equal to or less than the upper limit may have improvedworkability in producing a light-emitting device.

Light-Emitting Device

The light-emitting device includes a fluorescent member containing thefluorescent material (hereinafter also referred to as “first fluorescentmaterial”) and a resin, and a light-emitting element having a peakemission wavelength in a wavelength range of 380 nm to 470 nm. Combiningthe fluorescent member including the fluorescent material with alight-emitting element can provide a highly durable light-emittingdevice. The fluorescent member may further include a second fluorescentmaterial having a peak emission wavelength in a wavelength range of 500nm to 580 nm.

A light-emitting device 100 according to an embodiment of the presentdisclosure will now be described with reference to FIG. 3. FIG. 3 is aschematic cross-sectional view of the light-emitting device 100. Thelight-emitting device 100 is an example of a surface mounting typelight-emitting device. The light-emitting device 100 includes alight-emitting element 10 formed from a gallium nitride compoundsemiconductor, and a molded body 40 on which the light-emitting element10 is disposed. The light-emitting element 10 emits visible light atshort-wavelengths (e.g., a range of from 380 nm to 485 nm) and has apeak emission wavelength in the range of 430 nm to 470 nm. The moldedbody 40 includes a first lead 20 and a second lead 30, and a resinportion 42 including a thermoplastic or thermosetting resin in anintegral manner. The molded body 40 has a recess defined by a bottomsurface and side surfaces, and the light-emitting element 10 is disposedon the bottom surface of the recess. The light-emitting element 10 has apair of electrodes, positive and negative, and the positive and negativeelectrodes are electrically connected to the first lead 20 and thesecond lead 30, respectively, with a wire 60. The light-emitting element10 is covered with a fluorescent member 50. As shown in FIG. 3, thefluorescent member 50 includes, for example, a first fluorescentmaterial 71 and a second fluorescent material 72 as a fluorescentmaterial 70, and a resin.

The fluorescent member 50 serves not only as a member to convert thewavelength of light emitted from the light-emitting element 10, but alsoas a member to protect the light-emitting element 10 from the outsideenvironment. In FIG. 3, the particles of the fluorescent material 70 areunevenly dispersed in the fluorescent member 50. Arranging the particlesof the fluorescent material 70 closer to the light-emitting element 10in this manner allows the fluorescent material 70 to efficiently convertthe wavelength of light from the light-emitting element 10 so as toprovide a light-emitting device with high light-emitting efficiency. Itshould be noted, however, that the arrangement of the fluorescent member50 including the particles of the fluorescent material 70 and thelight-emitting element 10 is not limited to one in which they are inclose proximity to each other, and the particles of the fluorescentmaterial 70 may be arranged spaced apart from the light-emitting element10 within the fluorescent member 50 to avoid the influence of heat onthe fluorescent material 70. The fluorescent material 70 may also beapproximately evenly dispersed in the entire fluorescent member 50 toobtain light with reduced color unevenness.

Light-Emitting Element

The peak emission wavelength of the light-emitting element is in therange of 380 nm to 470 nm, preferably in the range of 440 nm to 460 nm,and more preferably in the range of 445 nm to 455 nm in consideration ofthe emission efficiency of the light-emitting device. A light-emittingdevice that emits mixed light of light from light-emitting element andfluorescent light from the fluorescent material is formed using such alight-emitting element as an excitation light source.

The half bandwidth of the emission spectrum of the light-emittingelement can be, for example, 30 nm or less. For the light-emittingelement, a semiconductor light-emitting element, such as an LED, ispreferably used. Using a semiconductor light-emitting element as thelight source may provide a highly efficient light-emitting device thathas high output linearity to the input and is resistant and stable tomechanical impact. As the semiconductor light-emitting element, forexample, a semiconductor light-emitting element that includes a nitridesemiconductor (In_(X)Al_(Y)Ga_(1−X−Y)N, wherein X and Y satisfy 0≦X,0≦Y, and X+Y≦1) and emits blue light may be used.

Fluorescent Member

The light-emitting device includes a fluorescent member containing thefirst fluorescent material and a resin. The fluorescent member, forexample, covers the light-emitting element to form a light-emittingdevice. The details of the first fluorescent material are as describedabove, and preferred embodiments of the first fluorescent material arealso as described above. Examples of the resin to be included in thefluorescent member include thermoplastic resins and thermosettingresins. Specific examples of thermosetting resins include modifiedsilicone resins, such as epoxy resins, silicone resins, andepoxy-modified silicone resins. Examples of the silicone resin includeat least one selected from the group consisting of methyl silicone,dimethyl silicone, methyl phenyl silicone, phenyl silicone, diphenylsilicone, and fluorosilicone.

The first fluorescent material content of the fluorescent memberrelative to the amount of the resin is, for example, 2% by mass or more,preferably 10% by mass or more, more preferably 40% by mass or more,and, for example, 190% by mass or less, preferably 160% by mass or less,and more preferably 130% by mass or less.

In addition to the first fluorescent material, the light-emitting devicemay include in the fluorescent member at least one second fluorescentmaterial having a different peak emission wavelength from that of thefirst fluorescent material. The light-emitting device having the secondfluorescent material can emit light of various color hues.

Specifically, the second fluorescent material can be a fluorescentmaterial having a composition represented by any one of the followingformulas (I) to (IX) below. These second fluorescent materials may beused alone or two or more in combination. As a second fluorescentmaterial having a peak emission wavelength in the range of 500 nm to 580nm, for example, at least one selected from the group consisting of thefluorescent materials represented by formulae (IV), (V), (VII), and(VIII) may be used. In particular, to produce a liquid crystal displaywith an improved color reproducibility, for example, selecting afluorescent material having a composition represented by formula (V) or(VII) as a second fluorescent material to be included in the fluorescentmember together with the first fluorescent material is preferable,rather than selecting a fluorescent material having a compositionrepresented by formula (VIII). To produce a light-emitting device havinghigh emission efficiency, selecting, as a second fluorescent material, afluorescent material having a composition represented by formula (VIII)is preferable.

(Ca_(1−p−q)Sr_(p)Eu_(q))AlSiN₃   (I)

In formula (I), p and q satisfy 0≦p≦1, 0<q<1, and p+q<1.

(Ca_(1−r−s −t)Sr_(r)Ba_(s)Eu_(t))₂Si₅N₈   (II)

In formula (II), r, s, and t satisfy 0≦r≦1, 0≦s≦1, 0<t<1, and r+s+t<1.

(i−j)MgO.(j/2)Sc₂O₃.kMgF₂. mCaF₂.(1−n)GeO₂.(n/2)M^(t) ₂O₃:zMn⁴⁺  (III)

In formula (III), M^(t) is at least one selected from the groupconsisting of Al, Ga, and In; and j, k, m, n, and z each satisfy 2≦i≦4,0<k<1.5, 0<z<0.05, 0<j<0.5, 0<n<0.5, and 0<m<1.5.

M¹¹ ₈MgSi₄O₁₆X¹¹ ₂:Eu   (IV)

In formula (IV), M¹¹ is at least one selected from the group consistingof Ca, Sr, Ba, and Zn; and X¹¹ is at least one selected from the groupconsisting of F, Cl, Br, and I.

Si_(6−z)Al_(z)O_(z)N_(8−z):Eu   (V)

In formula (V), z satisfies 0<z<4.2.

M_(m/n)Si_(12−(m+n))Al_((m+n))O_(n)N_((16−n)):EU   (VI)

In formula (VI), M is at least one selected from the group consisting ofSr, Ca, Li, and Y; n is 0 to 2.5; m is 0.5 to 5; n is an electric chargeof M; and x is 0.75 to 1.5.

M¹³Ga₂S₄:Eu   (VII)

In formula (VII), M¹³ is at least one selected from the group consistingof Mg, Ca, Sr, and Ba.

(Y,Gd,Tb,Lu)₃(Al,Ga)₅O₁₂:Ce   (VIII)

M^(a) _(V)M^(b) _(W)M^(c) _(X)Al_(3−y)Si_(y)N_(z)   (IX)

In formula (IX), M^(a) is at least one element selected from the groupconsisting of Ca, Sr, Ba, and Mg; M^(b) is at least one element selectedfrom the group consisting of Li, Na, and K; M^(c) is at least oneelement selected from the group consisting of Eu, Ce, Tb, and Mn; and v,w, x, y, and z each satisfy 0.80≦v≦1.05, 0.80≦w≦1.05, 0.001<x≦0.1,0<y≦0.5, 3≦z≦5.

When the light-emitting device includes a fluorescent member containinga second fluorescent material and a resin, the second fluorescentmaterial content relative to the amount of the resin is, for example, 1%by mass or more, preferably 5% by mass or more, and more preferably 10%by mass or more, and, for example, 200% by mass or less, preferably 150%by mass or less, and more preferably 100% by mass or less.

The fluorescent member may include other components as appropriate, inaddition to the fluorescent material and the resin. Examples of theother components include a filler, such as silica, barium titanate,titanium oxide, and aluminium oxide; a light stabilizer; and a colorant.When the fluorescent member includes other components, the amount to becontained may be appropriately selected in accordance with the purpose,for example. When, for example, a filler is included as one of suchother components, the amount to be contained may be 0.01% by mass to 20%by mass relative to the resin.

EXAMPLES

The present invention will now be described with reference to theExamples below; however, the present invention is not limited to theseExamples.

Method for Producing Fluorescent Material Particles

16.25 g of K₂MnF₆ was weighed and dissolved into 1000 g of a 55% by massHF aqueous solution to prepare Solution A. 195.10 g of KHF₂ was weighedand dissolved into 200 g of a 55% by mass HF aqueous solution to prepareSolution B.

450 g of a 40% by mass H₂SiF₆ aqueous solution was weighed and used asSolution C. Subsequently, Solution B and Solution C were each addeddropwise to Solution A with stirring at room temperature over about 20min. The resulting precipitate was solid-liquid separated, and thenwashed with isopropyl alcohol (IPA) and dried at 70° C. for 10 hours toprepare fluorescent material particles (core particles) containing afluoride having a composition represented by formula (1).

Example 1

102.6 g of a sodium salt solution of phosphoric acid (phosphoric acidconcentration: 2.4% by mass) and 2.5 g of a 30% by mass hydrogenperoxide solution were placed in a beaker. To this, pure water was addedto make a total weight of 150 g. Into this, 50 g of the prepared coreparticles was introduced with stirring to obtain a fluorescent materialslurry. To this fluorescent material slurry, 20 g of a lanthanum nitratesolution (lanthanum concentration: 5.0% by mass) was added and stirredwell. Lanthanum phosphate was observed to be precipitated in thefluorescent material slurry. The fluorescent material slurry was thendehydrated by filtering, and dried to obtain Fluorescent material 1 asintended. Lanthanum adhering to Fluorescent material 1 in the form oflanthanum phosphate constituted 1.1% by mass of Fluorescent material 1.

Example 2

256.4 g of a sodium salt solution of phosphoric acid (phosphoric acidconcentration: 2.4% by mass) and 2.5 g of a 30% by mass hydrogenperoxide solution were placed in a beaker. Into this, 50 g of theprepared core particles was introduced with stirring to obtain afluorescent material slurry. To this fluorescent material slurry, 50 gof a lanthanum nitrate solution (lanthanum concentration: 5.0% by mass)was added and stirred well. Lanthanum phosphate was observed to beprecipitated in the fluorescent material slurry. The fluorescentmaterial slurry was then dehydrated by filtering, and dried to obtainFluorescent material 2 as intended. Lanthanum adhering to Fluorescentmaterial 2 in the form of lanthanum phosphate constituted 2.9% by massof Fluorescent material 2.

Example 3

Fluorescent material 3 was obtained in the same manner as Example 2except that the amount of the sodium salt solution of phosphoric acid(phosphoric acid concentration: 2.4% by mass) was changed to 512.8 g;and that the amount of the lanthanum nitrate solution (lanthanumconcentration: 5.0% by mass) was changed to 100 g. Lanthanum adhering toFluorescent material 3 in the form of lanthanum phosphate constituted4.8% by mass of Fluorescent material 3.

Example 4

Fluorescent material 4 was obtained in the same manner as Example 3except that the amount of the sodium salt solution of phosphoric acid(phosphoric acid concentration: 2.4% by mass) was changed to 1025.6 g;and that the amount of the lanthanum nitrate solution (lanthanumconcentration: 5.0% by mass) was changed to 200 g. Lanthanum adhering toFluorescent material 4 in the form of lanthanum phosphate constituted6.7% by mass of Fluorescent material 4.

Comparative Example 1

As Fluorescent material C1 of Comparative Example 1, the prepared coreparticles were used as they are.

Comparative Example 2

100 g of the core particles and 9.5 g of calcium pyrophosphate powderwere added to 180 g of ethanol, and were suspended therein. To this,36.0 g of pure water and 36.0 g of Si(OEt)₄ were added, and 43.2 g ofammonia water was further added as a catalyst to cause hydrolysis.Subsequently, dehydration and drying treatments were carried out, andFluorescent material C2 was obtained. Fluorescent material C2 includesthe fluorescent material particles whose surfaces are coated withcalcium pyrophosphate using silica dioxide by sol-gel method. Calciumadhering to Fluorescent material C2 in the form of calcium phosphateconstituted 2.0% by mass of Fluorescent material C2.

Example 5

25.64 g of a sodium salt solution of phosphoric acid (phosphoric acidconcentration: 2.4% by mass) and 2.5 g of a 30% by mass hydrogenperoxide solution were placed in a beaker. To this, pure water was addedto make a total weight of 150 g. Into this, 50 g of the prepared coreparticles was introduced with stirring to obtain a fluorescent materialslurry. To this fluorescent material slurry, 30 g of a lanthanum nitratesolution (lanthanum concentration: 5.0% by mass) was added and stirredwell. Lanthanum phosphate was observed to be precipitated in thefluorescent material slurry. The fluorescent material slurry was thendehydrated by filtering, and dried to obtain Fluorescent material 5 asintended. Lanthanum adhering to Fluorescent material 5 in the form oflanthanum phosphate constituted 2.3% by mass of Fluorescent material 5.

Example 6

Fluorescent material 6 was obtained in the same manner as Example 5except that the amount of the sodium salt solution of phosphoric acid(phosphoric acid concentration: 2.4% by mass) was changed to 51.28 g;that pure water was added to make a total weight of 300 g; and that theamount of the lanthanum nitrate solution (lanthanum concentration: 5.0%by mass) was changed to 60 g. Lanthanum adhering to Fluorescent material6 in the form of lanthanum phosphate constituted 5.2% by mass ofFluorescent material 6.

Example 7

Fluorescent material 7 was obtained in the same manner as Example 5except that the amount of the sodium salt solution of phosphoric acid(phosphoric acid concentration: 2.4% by mass) was changed to 76.91 g;that pure water was added to make a total weight of 450 g; and that theamount of the lanthanum nitrate solution (lanthanum concentration: 5.0%by mass) was changed to 90 g. Lanthanum adhering to Fluorescent material7 in the form of lanthanum phosphate constituted 7.6% by mass ofFluorescent material 7.

Example 8

Fluorescent material 8 was obtained in the same manner as Example 5except that the amount of the sodium salt solution of phosphoric acid(phosphoric acid concentration: 2.4% by mass) was changed to 102.55 g;that pure water was added to make a total weight of 600 g; and that theamount of the lanthanum nitrate solution (lanthanum concentration: 5.0%by mass) was changed to 120 g. Lanthanum adhering to Fluorescentmaterial 8 in the form of lanthanum phosphate constituted 9.7% by massof Fluorescent material 8.

Example 9

Fluorescent material 9 was obtained in the same manner as Example 5except that the amount of the sodium salt solution of phosphoric acid(phosphoric acid concentration: 2.4% by mass) was changed to 128.19 g;that pure water was added to make a total weight of 750 g; and that theamount of the lanthanum nitrate solution (lanthanum concentration: 5.0%by mass) was changed to 150 g. Lanthanum adhering to Fluorescentmaterial 9 in the form of lanthanum phosphate constituted 12.0% by massof Fluorescent material 9.

Preparation of Light-Emitting Device a

Light-emitting devices a, or Examples 1a to 4a and Comparative Examples1a and 2a, were prepared respectively using Fluorescent materials 1 to 4obtained in Examples 1 to 4 and Fluorescent materials Cl and C2 obtainedin Comparative Examples 1 and 2, with another fluorescent material(second fluorescent material) having a composition of Y₃Al₅O₁₂:Ce in amanner as described below.

The ratio of each first fluorescent material, Fluorescent material 1, 2,3, or 4, or C1 or C2, to the second fluorescent material was adjusted toallow the light emitted by the light-emitting device a to havechromaticity coordinates around x=0.380 and y=0.380. Each firstfluorescent material and the second fluorescent material were added to asilicone resin, mixed and dispersed, and then defoamed to have a resincomposition. The resin composition was then poured onto a light-emittingelement in an LED package (peak emission wavelength: 455 nm) to fill therecess, followed by heating at 150° C. for 4 hours to cure the resincomposition.

Durability Evaluation

The resultant light-emitting devices a were lighted continuously with anelectric current of 250 mA in an environment tester at a temperature ashigh as 85° C. The evaluation was made by determining the amounts ofdifferences, Δx, Δy, in values x and y in chromaticity coordinatesbetween their initial values and the values after 700 hours of lighting.In the same manner, the relative light flux of each light-emittingdevice was also evaluated. A relative light flux as used herein is avalue of the light flux after 700 hours of lighting relative to theinitial value of the light flux, taking the initial value as 100. Table1 shows the evaluation results.

TABLE 1 Light Content of 700 hr (85° C., 250 mA) emitting Fluorescent LaRelative light flux device material (mass %) Δx Δy (%) Example 1aFluorescent 1.1 −0.01 0 81 material 1 Example 2a Fluorescent 2.9 −0.01 067 material 2 Example 3a Fluorescent 4.8 −0.01 0 80 material 3 Example4a Fluorescent 6.7 −0.01 0 76 material 4 Comparative Fluorescent — 0.040.07 59 Example 1a material C1 Comparative Fluorescent — −0.01 0.01 80Example 2a material C2

Table 1 shows that in each of the light-emitting devices of Examples 1ato 4a, Δy is zero, that is, there is no change in the value y from theinitial value in chromaticity coordinates. This indicates that thelight-emitting devices of Examples 1a to 4a are more durable thanComparative Examples 1a and 2a. Examples 1a to 4a only differ fromComparative Example 2a in value Δy by the amount of 0.01 numerically.However, this difference in color tone is significant to the naked eye.

FIGS. 1A and 1B show SEM images of Fluorescent material 1, and FIGS. 2Aand 2B show SEM images of Fluorescent material C1. Comparison of FIGS.1A and 1B with FIGS. 2A and 2B shows that lanthanum phosphate is adheredto the surfaces of the core particles in the form of at least particlesor a film in Fluorescent material 1. This structure causes strongadhesion between Fluorescent material 1 and the resin in the fluorescentmember, and this strong adhesion is considered to be responsible forhigh durability of the light-emitting devices including the fluorescentmember.

Preparation of Light-Emitting Device b

Light-emitting devices b, or Examples 5b to 9b and Comparative Example1b, were prepared respectively using Fluorescent materials 5 to 9obtained in Examples 5 to 9 and Fluorescent material C1 obtained inComparative Example 1, with another fluorescent material (secondfluorescent material) having a composition of Sr_(0.88)Eu_(0.12)Ga₂S₄ ina manner as described below.

The ratio of each first fluorescent material, i.e., Fluorescent material5, 6, 7, 8, or 9 or C1, to the second fluorescent material was adjustedto allow the light emitted by the light-emitting device to havechromaticity coordinates around x=0.280, y=0.270. Each first fluorescentmaterial, the second fluorescent material, and nanoparticles of silicawere added to a silicone resin, mixed and dispersed, and then defoamedto have a resin composition. The resin composition was then poured ontoa light-emitting element in an LED package (peak emission wavelength:455 nm) to fill the recess. The resin composition then underwentcentrifugal sedimentation to allow the fluorescent material particles tosettle. Further, the resin composition was cured with heating at 150° C.for 4 hours.

Durability Evaluation

The resultant light-emitting devices b were stored in an environmenttester at a temperature of 85° C. and a relative humidity of 85% withoutlighting them. After 1000 hours of storage, the light-emitting devices bwere lighted with an electric current of 20 mA. The evaluation was madeby determining the amounts of difference, Δx, Δy, between their initialvalues x and y in chromaticity coordinates before storage and after 1000hours of storage. In the same manner, the relative light flux of eachlight-emitting device was also evaluated. A relative light flux as usedherein is a value of the light flux after 1000 hours of storage relativeto the initial value of the light flux, taking the initial value as 100.Table 2 shows the evaluation results.

TABLE 2 1000 hr (85° C., 85% RH) Content Relative Light emittingFluorescent of La light flux device material (mass %) Δx Δy (%) Example5b Fluorescent 2.3 −0.003 −0.008 89 material 5 Example 6b Fluorescent5.2 −0.001 −0.004 91 material 6 Example 7b Fluorescent 7.6 −0.001 −0.00194 material 7 Example 8b Fluorescent 9.7 −0.001 0.000 93 material 8Example 9b Fluorescent 12.0 −0.002 −0.004 92 material 9 ComparativeFluorescent — −0.003 −0.011 88 Example 1b material C1

Table 2 shows that in each of the light-emitting devices of Examples 5bto 9b, the absolute value of Δy is smaller than that of ComparativeExample 1b. That is, the change in value y from the initial value inchromaticity coordinates is smaller. This indicates that thelight-emitting devices of Examples 5b to 9b have higher storagedurability than Comparative Example 1b in an environment at a hightemperature with a high humidity. The relative light fluxes are alsohigher than that of Comparative Example 1b.

The production method according to the present disclosure provides ahighly durable fluorescent material. The fluorescent material of thepresent disclosure can be used for a light-emitting device, and a highlydurable light-emitting device according to the present disclosure may beused in a variety of applications including displays, light sources forbacklighting, general lighting, in-vehicle lighting, using alight-emitting diode as an excitation light source.

It is to be understood that although the present invention has beendescribed with regard to preferred embodiments thereof, various otherembodiments and variants may occur to those skilled in the art, whichare within the scope and spirit of the invention, and such otherembodiments and variants are intended to be covered by the followingclaims.

Although the present disclosure has been described with reference toseveral exemplary embodiments, it is to be understood that the wordsthat have been used are words of description and illustration, ratherthan words of limitation. Changes may be made within the purview of theappended claims, as presently stated and as amended, without departingfrom the scope and spirit of the disclosure in its aspects. Although thedisclosure has been described with reference to particular examples,means, and embodiments, the disclosure may be not intended to be limitedto the particulars disclosed; rather the disclosure extends to allfunctionally equivalent structures, methods, and uses such as are withinthe scope of the appended claims.

One or more examples or embodiments of the disclosure may be referred toherein, individually and/or collectively, by the term “disclosure”merely for convenience and without intending to voluntarily limit thescope of this application to any particular disclosure or inventiveconcept. Moreover, although specific examples and embodiments have beenillustrated and described herein, it should be appreciated that anysubsequent arrangement designed to achieve the same or similar purposemay be substituted for the specific examples or embodiments shown. Thisdisclosure may be intended to cover any and all subsequent adaptationsor variations of various examples and embodiments. Combinations of theabove examples and embodiments, and other examples and embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the description.

In addition, in the foregoing Detailed Description, various features maybe grouped together or described in a single embodiment for the purposeof streamlining the disclosure. This disclosure may be not to beinterpreted as reflecting an intention that the claimed embodimentsrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter may bedirected to less than all of the features of any of the disclosedembodiments. Thus, the following claims are incorporated into theDetailed Description, with each claim standing on its own as definingseparately claimed subject matter.

The above disclosed subject matter shall be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments which fall within thetrue spirit and scope of the present disclosure. Thus, to the maximumextent allowed by law, the scope of the present disclosure may bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

All publications, patent applications, and technical standards mentionedin this specification are herein incorporated by reference to the sameextent as if each individual publication, patent application, ortechnical standard was specifically and individually indicated to beincorporated by reference.

What is claimed is:
 1. A method for producing a fluorescent materialcomprising: preparing fluorescent material particles comprising afluoride having a composition comprising Mn, at least one selected fromthe group consisting of alkali metal elements and NH₄ ⁺, and at leastone selected from the group consisting of Group 4 elements and Group 14elements; causing at least one cation selected from rare-earth elementsand a phosphate ion to come into contact with each other in a liquidmedium containing the fluorescent material particles to obtainrare-earth phosphate-adhered fluorescent material particles includingthe fluorescent material particles to which the rare-earth phosphate isadhered; and separating the rare-earth phosphate-adhered fluorescentmaterial particles from the liquid medium.
 2. The method according toclaim 1, wherein the liquid medium comprises the phosphate ion, and theliquid medium and a solution containing the cation are mixed to causethe cation and the phosphate ion to come into contact with each other.3. The method according to claim 1, further comprising mixing thefluorescent material particles and a liquid medium comprising thephosphate ion and a reducing agent to obtain the liquid mediumcontaining the fluorescent material particles.
 4. The method accordingto claim 3, wherein the reducing agent comprises hydrogen peroxide. 5.The method according to claim 1, wherein the fluoride has a compositionrepresented by formula (1):A₂[M_(1−p)Mn⁴⁺ _(p)F₆]  (1) wherein A is at least one selected from thegroup consisting of alkali metal elements and NH₄ ⁺; M is at least oneselected from the group consisting of Group 4 elements and Group 14elements; and p satisfies 0<p<0.2.
 6. A fluorescent material comprising:fluorescent material particles comprising a fluoride having acomposition comprising Mn; at least one selected from the groupconsisting of alkali metal elements and NH₄ ⁺; and at least one selectedfrom the group consisting of Group 4 elements and Group 14 elements; anda rare-earth phosphate arranged on the fluorescent material particles.7. The fluorescent material according to claim 6, wherein thecomposition is represented by formula (1):A₂[M_(1−p)Mn⁴⁺ _(p)F₆]  (1) wherein A is at least one selected from thegroup consisting of alkali metal elements and NH₄ ⁺; M is at least oneselected from the group consisting of Group 4 elements and Group 14elements; and p satisfies 0<p<0.2.
 8. The fluorescent material accordingto claim 6, wherein the composition comprises at least K and Si.
 9. Thefluorescent material according to claim 6, wherein the rare-earthphosphate comprises lanthanoid.
 10. The fluorescent material accordingto claim 9, wherein the lanthanoid is at least one selected from thegroup consisting of La, Ce, Dy, and Gd.
 11. The fluorescent materialaccording to claim 6, wherein the rare-earth metal element content ofthe rare-earth phosphate ranges from 0.1% by mass to 20% by mass.
 12. Alight-emitting device comprising: a fluorescent member comprising afirst fluorescent material and a resin; and a light-emitting elementhaving a peak emission wavelength in a wavelength range of 380 nm to 470nm, wherein the first fluorescent material comprises the fluorescentmaterial according to claim
 6. 13. The light-emitting device accordingto claim 12, wherein the fluorescent member further comprises a secondfluorescent material having a peak emission wavelength in a wavelengthrange of 500 nm to 580 nm.